Field of the Invention
The present invention relates to a touch screen, a touch panel including the touch screen, a display, and an electronic apparatus.
Description of the Background Art
Touch panels, which detect the touch by a pointer, such as a finger, and identify the touched position coordinates, have received attention as one of the excellent input means. In general, a touch panel includes a touch screen with a touch sensor embedded therein and a detector that identifies the touched position coordinates on the basis of a signal from the touch screen. The touch panels employing various detection methods including the resistive film method and the capacitive method have been introduced commercially.
One type of the touch panel employing the capacitive method is the projected capacitive touch panel (see, for example, Japanese Patent Application Laid-Open No. 2012-103761). The projected capacitive touch panel is capable of detecting the touch if the front surface of the touch screen with the touch sensor embedded therein is covered by the protective plate, such as a glass plate having the thickness of several millimeters. Therefore, such projected capacitive touch panel has the excellent ruggedness. The projected capacitive touch panel is also capable of detecting the touched position via the glove and includes no moving parts, thus having a long life.
The projected capacitive touch panel includes, as the detection electrodes to detect the capacitance, the first detection electrodes formed on the thin dielectric film in the row direction and the second detection electrodes formed over the first detection electrodes via the interlayer insulating film in the column direction. The detection electrodes do not have an electrical contact therebetween and include a plurality of intersection points formed via the dielectric film.
The projected capacitive touch panels can be classified into the touch panels employing the self-capacitance detection method and the touch panels employing the mutual capacitance detection method (see, for example, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 09-511086 (1997) and Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2003-526831). According to the self-capacitance method, the capacitance between the pointer, such as a finger, and the respective detection electrodes is detected to calculate the touched position coordinates. According to the mutual capacitance detection method, the position coordinates are calculated from the change in the capacitance between the detection electrodes caused by the pointer.
When the pointer, such as a finger, touches the planar region (detection cell) divided into a grid pattern by the first detection electrodes formed in the row direction and the second detection electrodes formed in the column direction, the touched position coordinates are identified from the proportion between the detected value in the detection cell and the detected value in the adjacent detection cell according to the self-capacitance detection method and the mutual capacitance detection method described above. The reduction in the interconnect resistance of the detection electrodes can increase the sensitivity of the touch screen. Thus, the detection electrodes each formed of the thin wire electrodes made of, for example, a metal having a low interconnect resistance substitute for the traditional detection electrodes formed of the thin-film transparent electrodes.
Assume that the first and second detection electrodes are formed of the metal thin-wire electrodes linearly extending in the row direction and in the column direction, respectively. In this case, the alignment direction of the pixels included in the liquid crystal display equipped with the touch screen becomes identical to the direction of the metal thin-wire electrodes included in the detection electrodes. If the pixel alignment and the repetition pitch of the thin wire electrodes have a certain relationship, the optical interference causes moire (interference fringes), considerably deteriorating the display quality. In a case where the detection electrodes include only the metal thin-wire electrodes extending in parallel in a single direction, the detectable area for the touch is unfortunately narrowed due to the occurrence of wire breakage.
Thus, the first and second detection electrodes extending in the row direction or in the column direction are formed of the thin wire electrodes having a mesh pattern in which the metal thin-wire electrodes obliquely inclined in different directions cross each other. Such detection electrodes including the thin wire electrodes having a mesh pattern extend in the direction that agrees with the pixel alignment direction. Meanwhile, the direction of the thin wire electrodes differs from the direction of the pixel alignment because the detection electrodes include the metal thin-wire electrodes inclined in the oblique direction. In addition, the repetition pitch can be adjusted. Therefore, the occurrence of moire can be prevented. Moreover, the thin wires are interconnected in a mesh pattern. Thus, the detection region is not narrowed when the wires are partly broken (see, for example, Japanese Patent Application Laid-Open No. 2010-97536).
However, the following problem arises when the lower layer of the polarizing plate on the front surface includes the touch screen in which the first and second detection electrodes extending in the row direction and the column direction are formed of the thin wire electrodes having a mesh pattern in which the metal thin-wire electrodes obliquely inclined in different directions cross each other. When the polarized light that is in parallel with or is perpendicular to the screen, in other words, the polarized light in the column direction or in the row direction enters the touch screen from the back surface, the polarization state of the incident light is changed by the thin wire electrodes having a mesh pattern and extending in the oblique direction. This allows the light that is to be absorbed in the polarizing plate on the front surface to penetrate the polarizing plate, unfortunately resulting in a light leakage.